The House of Representatives is expected to vote Tuesday on a civil contempt resolution against Attorney General William Barr and former White House counsel Don McGahn.
Here's what you need to know about what it means and how it came about:
Democrats vs. DOJ
Democrats, who control the majority in the House, want Barr to give them an unredacted copy of the report filed by former special counsel Robert Mueller on his Russia investigation.
They also want the underlying evidence that Mueller's office developed.
House Judiciary Committee Chairman Jerry Nadler, D-N.Y., issued a subpoena for the Mueller materials. Barr rejected it, recommending that President Trump withhold the documents under the doctrine of executive privilege, which lets a presidential administration conceal some of its internal workings.
The McGahn materials
The White House also invoked executive privilege to shield McGahn from talking to Congress or giving up documents.
The former White House counsel is a key part of episodes uncovered by Mueller's investigators. In one, Trump asked McGahn to remove Mueller and then, later, the president asked McGahn to cover up the earlier request.
Vote expected Tuesday
Nadler's committee has voted on contempt and, on Tuesday, the matter goes before all the members of the House. If the measure passes, it will authorize a civil lawsuit on behalf of the House.
Committee chairmen and women also would become empowered to file their own lawsuits in order to seek documents or testimony in investigations into Trump and administration officials.
Democrats are expected to support it. Republicans, who are a minority in the House, will oppose it. In fact, some Republicans may walk out in protest.
What is contempt?
A committee can issue a subpoena that's supposed to force a witness to give information or appear to testify. If a subject still doesn't agree, then that committee, or the full chamber, can find them in contempt.
But it isn't like a finding of contempt in court, in which a judge can order someone jailed if she or he won't cooperate. Capitol Police officers probably will not kick down Barr's door and haul him off to jail. Instead, the contempt vote means the House can file a lawsuit in which it asks a judge to order Barr to comply.
Why aren't Barr and McGahn cooperating?
Several reasons. The attorney general says the Justice Department has made as many accommodations as it can to permit members of Congress to see the parts of Mueller's report that were withheld from public view. Beyond that, the department says, Democrats are just picking a fight.
Specifically, federal regulations require the DOJ to keep grand jury material secret, Barr argues — even from Congress.
Politics also is at play, naturally: Barr is an ally of the president. And even before Trump came along, Barr spent his career as a champion for strong executive power. The Trump administration also says Mueller's report and resignation mean the Russia imbroglio is over and that America — and especially Democrats — must move on.
McGahn, meanwhile, may have broken with Trump, but he remains a loyal Republican and he and his lawyers have taken the position that he retains a duty to the president. So he's standing fast.
What do the members in the House say?
House Speaker Nancy Pelosi, Nadler and others argue that Mueller's office uncovered not only questionable actions, but criminal activity by Trump — alleged obstruction of justice in his attempts to frustrate the special counsel investigation.
The president's refusal to cooperate with investigations and subpoenas also could be an "impeachable offense," Pelosi has said.
Democrats, however, are divided among themselves about what action to take.
Some in the House support an inquiry that could lead to impeachment, the procedure by which Congress can remove a president from office. Presidents have been impeached before but never removed.
Pelosi is trying to both placate her most liberal members and keep mindful that many mainstream voters do not support impeachment. The Senate, meanwhile, remains under the control of Republicans. In impeachment, the House serves as a grand jury that recommends whether a president should be tried in the Senate, in proceedings overseen by the chief justice of the United States.
Trump enjoys support in the Senate
Republicans in the Senate probably would not vote to remove Trump from office. Some of Trump's supporters, in fact, believe that any impeachment process that did not result in removing Trump would be perceived as a victory for him — and a rebuke of Democrats.
So what Pelosi has chosen, in so many words, is a strategy in which Democrats try to inflict as much political punishment on Trump as they can short of impeachment, including with inquiries like the one that has brought the House to the brink of this week's contempt vote.
Some critics of Trump and Pelosi argue that the president's actions have been so egregious that the Congress has a duty under the Constitution to hold him to account irrespective of the political consequences for either side.
Has this ever happened before?
Big disputes often flare up when one or both houses of Congress are controlled by the party opposite from the one that holds the White House. And Congress has resorted to lawsuits in the past to try to compel the release of documents or the appearance for testimony of people who figured in its inquiries.
When will this case go to court?
Probably soon. Democrats have said they're optimistic about their chances, given past recognition by judges about the need for legislators to get information and exercise their powers of oversight.
Pelosi crowed in a news conference last week about the legal victories she said Democrats already have won in their attempts to get other information related to Trump, including bank and financial records.
What isn't clear, however, is how long the Barr matter might take to resolve. In former Attorney General Eric Holder's case, the litigation continued in one way or another until May of this year.
Going fast vs. going slow
The timing is important for the political aspects of the inquiries that Congress has launched.
Pelosi and the Democrats running for president next year would like to learn what they can about Trump's past practices as soon as possible to exploit everything they uncover ahead of Election Day.
Trump and the White House are seeking to block the House from getting the materials it has sought — by declining to cooperate with Congress and, in some cases, suing to quash the requests by Congress of third parties, such as Trump's banks.
The president and Republicans want to drag out these legal fights, to the degree they can, for as long as possible to keep whatever is in the records from becoming political fodder.